Answer:
$13.50
Explanation:
If I am taking off 40%, that means that the dress now cost 60% of the original cost. .6 x 20 is 12.
You could also calculate the 20% off and subtract that from the original cost. .4 x 20 =8. Now 20 - 8 is also 12.
Now, we have to calculate the tax. 10% of 12 is .1 x 12 or $1.20. We add the tax to the 12 to get 13.50.